1. Field of the Invention
The present invention relates to a novel copolymer and a water- and oil-repellent agent containing the same, and more particularly to a novel copolymer having a distinguished water- and oil-repellence and a water- and oil-repellent agent containing the same.
2. Related Art
Generally, copolymers having a water- and oil-repellence are copolymers each comprising a (meth)acrylate monomer containing a perfluoroalkyl group capable of directly giving a water- and oil-repellence, a fluorine-free monomer capable of improving an adhesiveness to the surfaces of materials to be treated such as fibers, etc. through an affinity thereto, and a monomer capable of giving a durability through self-crosslinking or reaction with reactive groups on the surface of the materials to be treated, typical of which are copolymers having chlorine atoms combined with the main chain, such as copolymers of perfluoroalkyl group-containing (meth)acrylate and vinyl chloride (JP-B-49-45758; JP-B-50-3438; JP-B-50-4800; JP-A-58-59277, etc.) and vinylidene chloride-based copolymers (JP-A-50-49179; JP-A-51-133511, etc.).
However, water- and oil-repellent agents comprising these copolymers have such drawbacks that unsaturated bonds are formed on the main chains by dehydrochlorination to give rise to a yellowing phenomenon more or less, which is an adverse effect on the treatment of the materials, on treated materials such as fibers, etc.
As to the yellowing mechanism observed in vinyl chloride-based or vinylidene chloride-based copolymers whose main chains are substituted with chlorine atoms, it is known that unsaturated bonds, if concentratedly formed in the polymers by dehydrochlorination reaction, can serve as conjugation sites and form chromophores due to such polyene structures Plastic Zairyo Koza (Plstic Material Lectures), Vol. 18, Vinyl chloride resin, pages 112-118, published by Nikkan Kogyo K. K., Japan!. Actually, the mechanism seems to takes more complicated decomposition steps.
The dehydrochlorination reaction is accelerated by high temperature treatment during the curing process in the presence of a cationic surfactant of emulsion dispersion type used in the preparation a water- and oil-repellent agent and cationic components in the antistatic agent or the softening agent using at the same time. Furthermore, in case of application on materials treated with some fluorescent dyes, a yellowing phenomenon, i.e. so called chlorine hindrance, occurs.
Copolymers having chlorine atoms as combined to the side chains are known, for example, copolymers having 2-chloroethyl vinyl ether as copolymerized (JP-B-49-45758). Such copolymers, when used as a water- and oil-repellent agent, can give a better feeling without causing any serious yellowing phenomenon, but still fail to satisfy desired properties such as applicability to natural fibers, shorter curing, etc. Likewise, 2-hydroxy-3-chloropropyl (meth)acrylate-based copolymers, etc. having chlorine atoms on the side chains have been so far used as a water- and oil-repellent agent (JP-A-55-45756), but have such disadvantages that feeling of stiffness will be more remarkable with increasing amount of the coplymers.